Ballack rescue act as Chelsea ride the shockwaves

Jose Mourinho last night escaped the Champions League defeat that could have hastened his departure as Chelsea's manager. He has Michael Ballack to thank for their continuing interest in the competition, the German repaying the depth of faith his manager has placed in him. After hinting on Monday that he will not be long of west London, Mourinho is setting about his legacy in this competition. It could yet be engraved on the European Cup.

Mourinho had spoken of his "prize motivation", how the fact that he would be in the Champions League's quarter-final and the FA Cup semi-finals "in five days" was driving him. Of course, it did not occur to the Chelsea manager that his team might not overcome Porto and Tottenham between last night and Sunday.

Yet in his near-three-year reign Chelsea have not lost a single match at home in the league, a record that extends back to his time as Porto's manager. The story is only slightly different in this competition, a single Stamford Bridge defeat having been sustained, and that against last year's European champions, Barcelona, last season. Indeed, having taken an away goal from the 1-1 draw in the first-leg trip to Porto, Mourinho's confidence seemed well placed.

Yet it could have proved an inglorious conceit. It has been too glibly stated John Terry's absence has cost Chelsea this season but last night it was certainly the case.

Defending higher up the pitch than they are accustomed to do with the England captain in their midst, Chelsea have become vulnerable to the long pass and Porto were ever alive to its potential.

With Claude Makelele too often static in the centre of midfield, Porto were passing it round him, a weakness that was compounded by Michael Essien's error. The Ghanaian seemed to forget that his role last night was as a central defender and not as the dynamic midfielder so beloved of Chelsea's fans.

Already advanced as high as the halfway line, Terry's replacement was sucked in to challenge Lucho Gonzalez. Essien was scrambling back to his post but Lucho played his perfectly measured pass through the gap that yawned between him and Ricardo Carvalho.

The Argentinian midfielder did not squander the opportunity. Ricardo Quaresma advanced on to his through ball and slipped it under Petr Cech to electrify this game. Chelsea seemed to be hit nervously with the shock. Ashley Cole, restored to the line-up despite the strong recent performances of Wayne Bridge, made an overlapping sprint up the left wing, searching for a return pass from Frank Lampard. But the England international played the ball into the hoardings, prompting Mourinho to rise from his seat and beseech his players to be calm.

Lampard was uncharacteristically hurried every time the ball reached him. The most costly such occasion was on the half- hour, when Andriy Shevchenko's centre found him eight yards out but the midfielder was unable to capitalise. Arjen Robben, who had made several spearing runs at the Porto defence, similarly lacked composure when, shortly before half-time, he set himself up on the edge of the area only to shoot well wide.

And all the while Chelsea's midfielders were giving the ball away too cheaply. Before this wastefulness, Chelsea had created their best first-half chance in the first minute. Shevchenko, a willing and effective runner last night, flicked on a header for Robben to collect.

The Dutchman - later booked for a shameful dive in the opposition box - pressured Fucile into giving away possession in the corner. Robben returned it to Shevchenko, whose bending shot swept marginally, agonisingly off target.

Mourinho addressed the possession problem by withdrawing Makelele for Mikel John Obi at the interval and advancing Lassana Diarra into midfield. The dividends were instant. Diarra pushed into the outside-right channel, dragging it back for the ubiquitous Robben.

The forward's speculative effort seemed well covered by Da Silva Helton at his near post, but the goalkeeper somehow allowed the ball to bobble over him for the equaliser. "I was cool because naturally if we don't score in the 48th minute we score in the 49th," said Mourinho. "It was our natural tendency to win the game because our experience would make sure."

From that moment, each time the ball approached Helton, who had twice dropped or ducked crosses, he was subjected to a crescendo of mocking that seemed utterly to unnerve him. On one occasion he slipped as he went to collect a back pass, on another he punched back to Chelsea a shot he should have held.

It all added to the growing drama of this fascinating encounter. Something would have to break, and Shevchenko's rising shot that flew a foot over the bar came two minutes before it did.

Cole's high diagonal ball found Drogba on the edge of the area. His header across goal for Shevchenko was returned to Ballack, who clinched the tie with just 11 minutes remaining with a hooked shot from close in.

"It's good for him because his goal has put Chelsea in the quarter-finals," said Mourinho. "Goals like that are like a stamp."